Opera, hands down. And I mean that almost literally.
Opera has this nifty little feature called Fast Forward, which in porn terms means one-handed browsing. Open a gallery, click an image. Hit space, until it scrolls to the bottom of the page. Hit space again, and what do you get? The next image in the gallery.

It’s like it was invented for this very purpose. I even know true FF buffs who switch to Opera whenever they’re watching porn.

I hope you can be unbiased enough to tell the poor guy that. I noticed someone recommended FF with the NoScript extension. The same functionality is built-in with Opera, so it’s ideal for porn – right out of the box.